The present invention relates generally to digital cameras, and more particularly, to a differential rate double shutter for use with cinematography digital image capture cameras.
In the past, conventional though the lens reflex cameras, and the like, have been developed to produce moving pictures. Typical of these are the well-known ArriFlex™ film camera, PanaFlex™ film camera, and Photosonics™ film camera, for example. In these conventional cameras, the requirement for a mechanical shutter limits the readout time available for electro-optic sensors, as read-out cannot begin until the sensor is fully occluded by the shutter resulting in an image integrate period, a transition period of lost time and a read-out period. Minimizing this transition period is a constraint on the image aperture size of the camera and therefore the resolution of the camera.
For example, at 24 frames per second, a complete integrate, transition, and read-out cycle is 41.67 milliseconds long for 360 degrees. If the maximum image integration period, referred to as shutter angle, is 180 degrees (20.83 milliseconds then the transition lost time and the read-out time must total 20.83 milliseconds. For larger high resolution arrays, this becomes difficult because the lost time increases as well as the read-out time, leading to the only alternative which is to decrease the shutter angle or image integration time.
Therefore, it is an objective of the present invention to provide for increased available shutter angle at the aperture by incorporating a differential rate double shutter for use with cinematography digital image capture cameras.